Smallest Number in Infinite Set

You have a set which contains all positive integers [1, 2, 3, 4, 5, ...].

Implement the SmallestInfiniteSet class:

SmallestInfiniteSet() Initializes the SmallestInfiniteSet object to contain all positive integers.
int popSmallest() Removes and returns the smallest integer contained in the infinite set.
void addBack(int num) Adds a positive integer num back into the infinite set, if it is not already in the infinite set.

class SmallestInfiniteSet: import heapq def __init__(self): self.summary = list(range(1, 1001)) heapq.heapify(self.summary) self.deleted = set() def popSmallest(self) -> int: A = heapq.heappop(self.summary) self.deleted.add(A) return A def addBack(self, num: int) -> None: if num in self.deleted: self.deleted.remove(num) heapq.heappush(self.summary, num)